CN112987488A - OPC correction method - Google Patents

OPC correction method Download PDF

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CN112987488A
CN112987488A CN202110196848.6A CN202110196848A CN112987488A CN 112987488 A CN112987488 A CN 112987488A CN 202110196848 A CN202110196848 A CN 202110196848A CN 112987488 A CN112987488 A CN 112987488A
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opc
model
precision
correction method
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CN112987488B (en
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张月雨
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Shanghai Huali Integrated Circuit Manufacturing Co Ltd
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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/36Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes

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  • General Physics & Mathematics (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Preparing Plates And Mask In Photomechanical Process (AREA)

Abstract

The invention discloses an OPC correction method, which comprises the following steps: step one, establishing a plurality of OPC models with different precisions; step two, providing a target layout needing OPC correction; selecting an OPC model with the lowest precision to perform multiple OPC operations on the target layout and forming a corresponding OPC intermediate layer; selecting an OPC model with a higher precision layer to perform OPC operation for multiple times on an OPC intermediate layer formed by the OPC model with the previous precision layer and forming a corresponding OPC intermediate layer; step five, repeating the step four until an OPC intermediate layer corresponding to the OPC model with the second highest precision is formed; and step six, selecting the OPC model with the highest precision, and carrying out multiple OPC operations on the OPC intermediate layer corresponding to the OPC model with the second highest precision to form a final OPC result. The invention can reduce the total OPC operation time under the condition of ensuring the correction precision.

Description

OPC correction method
Technical Field
The present invention relates to a semiconductor integrated circuit manufacturing method, and more particularly, to an Optical Proximity Correction (OPC) method.
Background
In the photoetching process, a graphic structure corresponding to a layout on a Mask, namely a photomask (Mask), is projected into a photoresist through an exposure system and forms a corresponding graphic structure in the photoresist, but due to optical reasons or chemical reactions of the photoresist in the exposure process, the graphic structure formed in the photoresist and the graphic structure on the Mask have deviation, the deviation needs to be corrected through OPC in advance to modify the graphic structure on the Mask, and when the Mask corrected through OPC is used for exposure, the graphic structure formed in the photoresist conforms to the designed graphic structure and meets the process production requirements.
The OPC includes Rule-based OPC and model-based OPC.
Early rule-based OPC was widely used due to its simplicity and fast computation. However, this method requires manual OPC rules, which become extremely cumbersome and difficult to follow as optical distortions become more severe.
At this time, model-based OPC should be generated. The model-based OPC method establishes an accurate calculation model through optical simulation, and then adjusts the edge of a graph to continuously simulate and iterate until the graph approaches to an ideal graph. Model-based OPC makes the OPC process more complex and the demand for computing resources grows exponentially.
With the development of the technical nodes, the smaller the pattern size is, the less the influence of the tiny physical effect on the lithography size can be ignored, and in order to realize the high-precision OPC model, the modeling parameters are more and more complicated, such as introducing more complicated physical effects like Mask3D, and the influence of the chemical effect of using more basis functions to fit the photoresist on the pattern size, and the like, wherein the Mask3D strictly models the electromagnetic wave scattered from the surface of the photomask to represent the influence of the Mask surface stereo structure on the light diffraction.
FIG. 1 is a flow chart of a conventional OPC correction method; the existing OPC correction method comprises the following steps:
step one, establishing a high-precision OPC model. With the reduction of technical nodes, the high-precision OPC model needs more and more factors to be considered, and if the influence of a tiny physical effect needs to be considered, modeling parameters are more and more complex. The high-precision OPC model needs to be established strictly according to the requirement of mass production.
And step two, providing a target layout needing OPC correction, wherein the graph of the target layout is in an initial state.
And thirdly, carrying out multiple OPC operations on the target layout by adopting a high-precision OPC model to form an OPC result and outputting the OPC result.
In the third step, because the parameters of the high-precision OPC model are complex, the OPC calculation amount can be obviously increased when the OPC model obtains high precision, the number of graphs in a unit area is increased in multiples along with the reduction of the graph size, and the OPC calculation time is almost multiplied, so that the method not only provides a serious challenge for the CPU calculation resource amount, but also for ensuring that the mask can be published on time.
Disclosure of Invention
The invention aims to provide an OPC correction method which can reduce the total OPC operation time under the condition of ensuring the correction precision.
In order to solve the above technical problem, the OPC correction method provided by the present invention includes the steps of:
step one, establishing a plurality of OPC models with different accuracies.
And step two, providing a target layout needing OPC correction, wherein the graph of the target layout is in an initial state.
And thirdly, selecting the OPC model with the lowest precision to perform multiple OPC operations on the target layout and forming an OPC intermediate layer corresponding to the OPC model with the lowest precision.
And fourthly, selecting the OPC model with the higher precision layer to perform multiple OPC operations on the OPC intermediate layer formed by the OPC model with the previous precision layer and form the OPC intermediate layer corresponding to the OPC model with the selected precision.
And step five, repeating the step four until an OPC intermediate layer corresponding to the OPC model with the second highest precision is formed.
And step six, selecting the OPC model with the highest precision, and carrying out multiple OPC operations on the OPC intermediate layer corresponding to the OPC model with the second highest precision to form a final OPC result.
The further improvement is that the step one comprises 2 OPC models with precision, and the step four and the step five are omitted.
The further improvement is that the OPC model with the highest precision is an OPC model which is built according to the mass production requirement and meets the specification.
The OPC model with the second highest precision or lower is an OPC model generated by simplifying model parameters or reducing the model calculation range on the basis of the OPC model with the highest precision; the OPC model having a smaller accuracy has a higher operation speed.
The further improvement is that the pattern period and the size are in the range of 1-2 times close to the minimum design pattern period and size, and the simulation trend of the OPC operation by adopting the OPC model with the accuracy lower than the second highest is consistent with the actual measurement data on the silicon substrate.
The further improvement is that the optimal solution of the OPC operation times corresponding to the OPC models with various accuracies in the third step, the fourth step and the fifth step is that the maximum total OPC operation time is saved while the final OPC result meeting the requirements is obtained.
In the sixth step, the number of OPC operations corresponding to the OPC model with the highest accuracy is 1 to 20, and the smaller the number of OPC operations corresponding to the OPC model with the highest accuracy, the more the total OPC operation time is saved.
The further improvement is that when the step one comprises 2 OPC models with the accuracy, the OPC operation times corresponding to the OPC model with the lowest accuracy in the step three are 1 to 15, and the optimal solution of the OPC operation times corresponding to the OPC model with the lowest accuracy is selected from 1 to 15.
The further improvement is that the final OPC result obtained in the sixth step meets the OPC precision requirement of mass production.
The invention can adopt the OPC model with lower precision to carry out OPC operation at the initial stage and adopt the OPC model with the highest precision to carry out OPC operation at the final stage by setting a plurality of OPC models with different precisions, and because the lower the precision of the OPC model is, the time of the OPC operation is less, the invention can accelerate the OPC operation speed by replacing the OPC model with the highest precision to carry out the OPC operation at the initial stage, thereby saving the OPC operation time.
Meanwhile, in the initial stage, although the accuracy of the OPC model with lower accuracy is lower, the OPC model still accords with the correction direction and the convergence direction from the initial state of the target layout to the final state of the final OPC result, so that under the condition of ensuring that the correction direction is not changed, the convergence can be accelerated, the final OPC result is ensured to accord with the accuracy requirement, and the accuracy of the final OPC result is still ensured by the OPC model with the highest accuracy, so the invention can ensure the correction accuracy.
Therefore, the invention can reduce the total OPC operation time under the condition of ensuring the correction precision.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1 is a flow chart of a prior art OPC correction method;
FIG. 2 illustrates an OPC correction method according to an embodiment of the present invention;
FIG. 3A is a schematic diagram of Edge Placement Error (EPE) after a first iteration of OPC operations using a highest-precision OPC model;
FIG. 3B is a schematic diagram of edge placement errors after a second iteration of OPC operations using the highest-precision OPC model.
Detailed Description
FIG. 2 shows an OPC correction method according to an embodiment of the present invention; the OPC correction method provided by the embodiment of the invention comprises the following steps of:
step one, establishing a plurality of OPC models with different accuracies.
In the embodiment of the invention, the OPC model with the highest precision is the OPC model which is established according to the mass production requirement and meets the specification.
The OPC model with the second highest precision or lower is generated by simplifying model parameters or reducing a model calculation range on the basis of the OPC model with the highest precision; the OPC model having a smaller accuracy has a higher operation speed.
The pattern period and the size are in the range of being close to 1-2 times of the minimum design pattern period and size, and the simulation trend of performing OPC operation by adopting an OPC model with the accuracy lower than the second highest is consistent with actual measurement data on a silicon substrate.
And step two, providing a target layout needing OPC correction, wherein the graph of the target layout is in an initial state.
And thirdly, selecting the OPC model with the lowest precision to perform multiple OPC operations on the target layout and forming an OPC intermediate layer corresponding to the OPC model with the lowest precision.
And fourthly, selecting the OPC model with the higher precision layer to perform multiple OPC operations on the OPC intermediate layer formed by the OPC model with the previous precision layer and form the OPC intermediate layer corresponding to the OPC model with the selected precision.
And step five, repeating the step four until an OPC intermediate layer corresponding to the OPC model with the second highest precision is formed.
In the embodiment of the invention, the optimal solution of the OPC operation times corresponding to the OPC models with various accuracies in the third step, the fourth step and the fifth step is that the maximum total OPC operation time is saved while the final OPC result meeting the requirements is obtained.
And step six, selecting the OPC model with the highest precision, and carrying out multiple OPC operations on the OPC intermediate layer corresponding to the OPC model with the second highest precision to form a final OPC result. The final OPC result meets the OPC precision requirement of mass production.
In a preferred embodiment, step one includes 2 precision OPC models and step four and step five are omitted. At this time, the number of OPC operations corresponding to the OPC model with the lowest accuracy in the third step is 1 to 15, and the optimal solution of the number of OPC operations corresponding to the OPC model with the lowest accuracy is selected from 1 to 15.
In the sixth step, the number of times of OPC operation corresponding to the OPC model with the highest precision is 1 to 20 times, and the smaller the number of times of OPC operation corresponding to the OPC model with the highest precision, the more the total OPC operation time is saved.
The effect of the method of the embodiment of the present invention on saving the total OPC operation time will now be described with reference to specific parameters:
the conventional method shown in fig. 1 can obtain an OPC result meeting the requirements by performing 8 OPC operations using a high-precision OPC model.
When the method of the embodiment of the invention adopts two OPC models, the OPC operation times of the OPC model with the lowest precision in the step three, namely the low-precision OPC model, are 5 times, and the OPC operation times of the OPC model with the highest precision in the step six are 5 times. And the OPC model with the highest precision in the step six is equal to the precision of the high-precision OPC model adopted by the existing method.
The relationship between the computation speeds of the low-accuracy OPC model and the high-accuracy OPC model is as follows:
carrying out simulation operation on the high-precision OPC model for about 38 minutes once;
carrying out simulation operation on the low-precision OPC model for about 8 minutes once;
the total OPC operation time of the existing OPC correction method is 8 × 38 to 304 minutes;
the total OPC operation time of the method is 5 × 8+5 × 38-230 minutes;
it can be seen that, although the total number of iterations of the method according to the embodiment of the present invention is greater than or equal to that of the conventional OPC correction method, the method according to the embodiment of the present invention can save about 24.4% of OPC operation time compared to the conventional method due to the advantage of the operation speed of the low-precision OPC model.
According to the method, the OPC models with lower precision can be adopted to carry out OPC operation at the initial stage through the arrangement of the OPC models with different precisions, the OPC model with the highest precision is adopted to carry out OPC operation at the final stage, and the lower the precision of the OPC model is, the less the time of the OPC operation is, so that the OPC operation is carried out by replacing the OPC model with the lower precision with the OPC model with the highest precision at the initial stage, the OPC operation speed can be accelerated, and the OPC operation time can be saved.
Meanwhile, in the initial stage, although the accuracy of the OPC model with lower accuracy is lower, the OPC model still accords with the correction direction, namely still accords with the convergence direction from the initial state of the target layout to the final state of the final OPC result, so that under the condition of ensuring that the correction direction is not changed, the convergence can be accelerated, the final OPC result is not influenced, and the accuracy of the final OPC result is still ensured by the OPC model with the highest accuracy, so that the method disclosed by the embodiment of the invention can ensure the correction accuracy. FIG. 3A is a schematic diagram of an edge placement error after a first iteration of OPC operations using the OPC model with the highest accuracy; fig. 3A shows target layer graphs 101 of a plurality of layouts, and after performing the first iterative OPC operation, the edges of the graphs 101 are corrected, and the OPC result simulation layer graphs after the edge correction are shown as a mark 102 a; fig. 3B is a schematic diagram of the edge placement error after the second iteration of OPC operations using the OPC model with the highest accuracy, and the simulated layer pattern of the OPC result after edge correction is shown as a mark 102B. It can be seen that in the initial correction stage, as shown in fig. 3A and 3B, the difference between the patterns 102a and 102B and the target layer pattern 101 is large, specifically, refer to the values in the dashed circles 103A and 103B, the dashed circles 104a and 104B, and the dashed circles 105a and 105B, respectively. It can be seen that, at the initial stage of OPC operation using the OPC model, after the pattern of the photomask is corrected, there is a large difference between the OPC correction result and the final convergence result, the pattern movement amount of the photomask of each loop iteration is related to the edge placement error, and when the edge placement error is large, the movement amount of the photomask pattern tends to approach the set upper limit value of single maximum movement, and at this time, only the Mask correction movement direction is required to be correct, and the accuracy degree of the movement amount does not significantly affect the final correction result, so that a low-accuracy OPC model can be used to perform rapid approximate simulation operation, and a more time-consuming high-accuracy OPC model is not required to perform simulation operation. When the correction result is close to the target after several iterative operations, the fineness of the movement amount is more important, a high-precision OPC model is needed to realize more precise correction, and finally, an OPC result which meets the requirements as the conventional OPC correction method can be obtained.
Therefore, the method of the embodiment of the invention can reduce the total OPC operation time under the condition of ensuring the correction precision.
The present invention has been described in detail with reference to the specific embodiments, but these should not be construed as limitations of the present invention. Many variations and modifications may be made by one of ordinary skill in the art without departing from the principles of the present invention, which should also be considered as within the scope of the present invention.

Claims (9)

1. An OPC correction method is characterized by comprising the following steps:
step one, establishing a plurality of OPC models with different precisions;
providing a target layout needing OPC correction, wherein the graph of the target layout is in an initial state;
selecting an OPC model with the lowest precision to perform multiple OPC operations on the target layout and forming an OPC intermediate layer corresponding to the OPC model with the lowest precision;
selecting an OPC model with a higher precision layer to perform multiple OPC operations on an OPC intermediate layer formed by the OPC model with the previous precision layer and form an OPC intermediate layer corresponding to the OPC model with the selected precision;
step five, repeating the step four until an OPC intermediate layer corresponding to the OPC model with the second highest precision is formed;
and step six, selecting the OPC model with the highest precision, and carrying out multiple OPC operations on the OPC intermediate layer corresponding to the OPC model with the second highest precision to form a final OPC result.
2. The OPC correction method of claim 1, wherein: the first step comprises 2 OPC models with precision, and the fourth step and the fifth step are omitted.
3. The OPC correction method of claim 1 or 2, characterized in that: the OPC model with the highest precision is the OPC model which is established according to the mass production requirement and meets the specification.
4. The OPC correction method of claim 3 wherein: the OPC model with the second highest precision or lower is generated by simplifying model parameters or reducing a model calculation range on the basis of the OPC model with the highest precision; the OPC model having a smaller accuracy has a higher operation speed.
5. The OPC correction method of claim 4 wherein: the pattern period and the size are in the range of being close to 1-2 times of the minimum design pattern period and size, and the simulation trend of performing OPC operation by adopting an OPC model with the accuracy lower than the second highest is consistent with actual measurement data on a silicon substrate.
6. The OPC correction method of claim 1 or 2, characterized in that: and the optimal solution of the OPC operation times corresponding to the OPC models with various accuracies in the third step, the fourth step and the fifth step is that the maximum total OPC operation time is saved while the final OPC result meeting the requirements is obtained.
7. The OPC correction method of claim 6 wherein: in the sixth step, the number of times of OPC operation corresponding to the OPC model with the highest precision is 1 to 20 times, and the smaller the number of times of OPC operation corresponding to the OPC model with the highest precision, the more the total OPC operation time is saved.
8. The OPC correction method of claim 6 wherein: when the first step comprises 2 OPC models with the lowest precision, the OPC operation times corresponding to the OPC model with the lowest precision in the third step are 1 to 15, and the optimal solution of the OPC operation times corresponding to the OPC model with the lowest precision is selected from 1 to 15.
9. The OPC correction method of claim 1 wherein: and the final OPC result obtained in the sixth step meets the OPC precision requirement of mass production.
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JP2004302263A (en) * 2003-03-31 2004-10-28 Sharp Corp Method for correcting mask pattern and photomask
US20080127027A1 (en) * 2006-11-02 2008-05-29 International Business Machines Corporation Printability verification by progressive modeling accuracy
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CN103631085A (en) * 2012-08-29 2014-03-12 中芯国际集成电路制造(上海)有限公司 Correction method for optical proximity correction model
CN103246153A (en) * 2013-04-28 2013-08-14 上海华力微电子有限公司 Territory map layer design method of semiconductor chip and mask plate thereof
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